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Unexplained Respiratory Disease Outbreaks (URDO)








Investigate an Outbreak						Print
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										Investigation into the clinical and epidemiologic features, as well as the etiology of outbreaks is particularly important to public health. Investigate severe unexplained respiratory outbreaks to rule out emerging health threats.
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			Defining an outbreak of unexplained respiratory illnessOutbreaks to investigateComponents for epidemiological investigation of outbreaksData collection formsBackground
		
Defining an outbreak of unexplained respiratory illness
A cluster is “an aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known.”
An **outbreak** is when there is more disease cases than what is usually expected:.
For a given time (e.g., within 2 weeks)
Within a specific location (e.g., linked by institution, affiliation, exposure, small geographic area)
For a target population (e.g., students, long-term care residents)Adjusting outbreak definition
As additional information about a particular outbreak becomes available, it may make sense to adjust the outbreak definition.
Consider incorporating:
Predominant clinical presentations (e.g., pneumonia, pharyngitis)
Severity of illness (e.g., hospitalizations, deaths)
Demographic profiles
Illness onset dates of the cases (see Line List Template [4 pages])
A comparison to the historical or baseline rates for similar disease in the communitySingle case evaluation
In certain situations, public health officials may need to evaluate a single case of unexplained respiratory disease as a possible outbreak. Examples include diseases with the potential need for immediate public health intervention (e.g., suspect pulmonary anthrax, plague, avian influenza, MERS, hantavirus pulmonary syndrome).
Outbreaks to investigate
For each respiratory disease outbreak, public health officials determine the appropriate level of public health response. They must consider many factors in making the decision, such as availability of resources and competing agency priorities. However, several characteristics of respiratory outbreaks typically warrant further investigation and an urgent response.
The characteristics below, while not comprehensive or definitive, can help **determine which outbreaks merit further investigation**:
Unknown etiology after initial work-up
Associated with severe disease manifestations, such as need for hospitalization or death
May be useful to answer epidemiologic, laboratory, or infection control questions
Possible vaccine-preventable diseases
Associated with congregate settings or with a likely (controllable) environmental source
Respiratory infection potentially caused by a bioterrorism agent
Outbreaks that have generated excessive public anxiety
Either very large or rapidly progressingSee Request CDC Assistance for guidance on when and how to reach out to CDC for help investigating an unexplained respiratory disease outbreak.
Components for epidemiological investigation of outbreaks
Below are some of the common components of an epidemiological outbreak investigation. The circumstances in any given outbreak may require additional steps.
**Start to collect information**
Begin collecting available epidemiologic, clinical, and laboratory information to help assess the situation. See Respiratory Outbreak Survey [1 page] for an example on the types of information you might want to gather.
The following tools will help guide the next steps:
Job-aid for developing a case definition [2 pages]
Line list template [4 pages]
Excel spreadsheet on generating an epidemiologic curve [2 sheets]
Guidelines for specimens collection and handling
**Develop public health response to outbreak**
The initial information gathered may lead to additional questions in order to gauge the degree of response.
The following steps may help inform an appropriate response:
Determine the number of cases and severity of disease
Assess the need and potential for interventions (e.g., cohorting, quarantine, vaccination, use of prophylaxis, elimination of potential disease source)
Consider the likelihood of natural versus intentional source of infection
Evaluate the level of public health, clinician, or community concern
**Report and respond**
Coordinate the public health response by:
Discussing with staff in your program (e.g., laboratory, epidemiology, environmental, veterinary, other personnel as appropriate)
Notifying appropriate local or state public health officials
Notifying CDC, if indicated, of the outbreak by e-mailing URDO (M-F; 8 am–4 pm EST) or calling the emergency, after-hours hotline at 770-488-7100.Data collection forms
Public health officials may wish to gather additional information about possible exposures using Data Collection Forms. These forms can assist in the interview and investigation of single cases of disease.
Adapt these forms to collect information relevant to identifying etiologies of respiratory outbreaks.
Do **not** use these forms to report a disease outbreak to CDC. For reporting assistance, please refer to your state health department.Background
Outbreak investigation importance
Outbreaks of acute respiratory illness are common and can occur in many settings (e.g., communities, nursing homes, military barracks). Specific therapies, infection control practices, and other preventive measures may be necessary to control outbreaks. Consequently, investigation into the clinical and epidemiologic features, as well as the etiology of outbreaks is particularly important to public health.
Investigating severe unexplained respiratory outbreaks may be of particular importance to rule out emerging health threats.
Clinical respiratory syndromes
Predominant clinical respiratory syndromes include outbreaks of
Prolonged paroxysmal cough
Bronchitis
Pneumonia
Influenza-like illness
Acute respiratory distress syndrome or rapidly progressive pneumoniaCoordinate outbreak investigations
Despite continual efforts, the etiology of many acute respiratory illnesses may remain unexplained. Investigating unexplained respiratory outbreaks may identify infectious agents that require unique strategies for control and prevention (e.g., hantavirus pulmonary syndrome, avian influenza). However, outbreak investigations for previously identified etiologies are equally important.
This process can be enhanced through coordinated efforts that:
**Alert clinicians** to identify and report cases and clusters of unexplained infectious diseases
**Prepare health departments** to investigate these clusters
**Guide laboratory scientists** to develop and apply both traditional and novel diagnostic approaches to define the organism-specific etiology of the outbreak
More informationEpidemiologic Curve
Data Collection Forms
Generate a Differential DiagnosisTop of Page
							
					
							Last Reviewed:  June 1, 2023						Source: 	National Center for Immunization and Respiratory Diseases, Division of Bacterial Diseases
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